Edit "Submit Listing" Destination URL

I have looked and cannot find the file referencing the destination link for the submit listing button on the Responsive Directory theme. Instead of sending users to /add-listing/ I want to send them to /wp-login.php?action=register

Otherwise, it creates a confusing loop for new users (which most of mine will be) My users will typically only be creating one listing. Therefore, as it is now, when they click “Submit Listing” button, it sends them to /add-listing. Then they must choose a package, which THEN sends them to log in screen, where they can register. Once registered, there’s no way to let them know they must click the submit listing button AGAIN to select their package.